Having visited numerous aquariums around the USA, I was pleasantly surprised recently by seeing a Hogfish in an aquarium in Chattanooga of all places.

They have a touch tank on the top floor for rays and skates. Lo and behold they have a medium sized Hogfish in the same shallow water tank. He was not allowing himself to be touched though.
Have a missed seeing Hogs in other seawater aquariums perhaps?

The Chattanooga seawater aquarium is IMHO mediocre, but their freshwater aquarium facility is first rate and the best I have seen so far. Incredible layout of tanks.
First place I have seen an African Tiger Fish in captivity.

From the salt water aquarium perspective, Cherryl and I were discussing what fish are not commonly seen.
For example has anyone seen:-
1. Cobia in an aquarium? (Saw one in Durban Aquarium, but cannot recall seeing any in the States)
2. Dorado?
3. Triple Tail (Labotes)

Last time I was there was a huge Goliath Grouper in the oil platform tank. It has been said that the curators were curios because a small school of 3-4 ft. Blacktip Sharks kept disappearing overnight when it was first set up. Later they learned that GG was having midnight hors d'oeuvres (pronounced "or devoured). Also some awesome Redfish (Red Drum) and Tarpon. A visit to the carrier USS Lexington is fun too.